In a medium saucepan over medium heat, combine sugar, corn syrup and vinegar. Cook, stirring, until sugar dissolves. Heat, without stirring, to 300 to 310 degrees F or until a small amount of syrup dropped into cold water forms hard, brittle threads.
Remove from heat and stir in baking soda.
Pour into prepared pan; do not spread. Mixture will not fill pan.
Allow to cool completely.
Melt morsels and shortening in medium, uncovered, microwave-safe bowl for 1 minute; stir. Microwave an additional 10 to 15 seconds, stirring until smooth.
Break cooled candy into bite sized pieces and dip into melted chocolate. Let set on waxed paper. Store tightly covered.